What is GH (General Hardness)?
GH, or General Hardness, measures the concentration of dissolved calcium and magnesium ions in your aquarium water. These aren’t just random minerals - they’re the building blocks your shrimp need to construct their exoskeletons. Without adequate GH, shrimp cannot form proper shells, leading to molting failures, deformities, and the dreaded White Ring of Death.
The “hardness” terminology comes from water’s historical use - hard water with high mineral content made it difficult to form soap lather. For shrimp keepers, hardness directly correlates with shell health and molting success.
Why GH is Critical for Shrimp
Every few weeks, your shrimp must shed their old exoskeleton and form a new, larger one - a process called molting. This is one of the most vulnerable moments in a shrimp’s life, and proper GH is essential for success:
The Molting Process
- Shrimp absorbs water to swell and crack the old shell
- It wriggles out of the old exoskeleton (takes minutes)
- The new soft shell begins hardening immediately
- Full hardening takes 24-48 hours
During step 3 and 4, the shrimp pulls calcium and magnesium from the water to mineralize its new shell. If these minerals aren’t available in sufficient quantities, the shell remains soft and vulnerable, or worse, the molt fails entirely.
The White Ring of Death
This fatal condition occurs when a shrimp begins molting but cannot complete it. A white band appears where the old shell started to separate, but the shrimp remains trapped. Causes include:
- Insufficient GH: Not enough calcium/magnesium for new shell
- Mineral imbalance: Wrong Ca:Mg ratio even if total GH is adequate
- Stress-induced molting: Temperature swings or parameter changes triggering premature molts
- Disease or weakness: Underlying health issues preventing successful molting
Once the white ring appears, it’s usually fatal within 24-72 hours. Prevention through proper GH maintenance is the only reliable approach.
GH and Different Shrimp Species
Neocaridina (Cherry Shrimp, etc.)
Neocaridina are adaptable and thrive in GH 6-12 dGH. They can often survive in even harder water, making them forgiving for beginners. Most tap water in regions with moderate hardness suits them without modification.
Caridina (Crystal Red, Taiwan Bee, etc.)
Caridina evolved in soft, mineral-poor waters and require much lower GH of 4-6 dGH. Higher GH stresses their osmotic regulation systems and interferes with breeding. These shrimp almost always require RO water remineralized to exact specifications.
Sulawesi Shrimp
Sulawesi shrimp come from ancient Indonesian lakes with unique water chemistry. They need GH 6-8 dGH with specific mineral compositions - standard remineralizers don’t work. Specialized Sulawesi mineral salts are required.
Signs of GH Problems
GH Too Low
- Failed molts and White Ring of Death
- Soft, flexible shells that dent when touched
- Pale, washed-out coloration
- Slow growth in juveniles
- Deaths concentrated around molting periods
GH Too High
- Thick, opaque shells (less concerning)
- Difficulty molting due to overly rigid shell
- Osmotic stress symptoms (lethargy, reduced breeding)
- More common in tap water users
The GH-TDS Relationship
GH contributes to TDS but doesn’t account for all of it. You can have correct GH with wrong TDS (organics, nitrates adding to TDS), or correct TDS with wrong GH (non-hardness minerals like sodium contributing to TDS).
Always test both GH and TDS - they tell different parts of the water quality story.
Recommended Remineralizers
Choosing the right remineralizer depends on your shrimp species and whether you need to adjust KH along with GH:
For Caridina (GH+ Only)
- Salty Shrimp Bee Shrimp Mineral GH+ - The gold standard for Crystal Red, Taiwan Bee, and other Caridina
- SL-Aqua Blue Wizard GH - Premium Taiwanese alternative with excellent results
- GlasGarten Mineral Junkie Pearls - Supplemental minerals in convenient pearl form
For Neocaridina (GH/KH+)
- Salty Shrimp Shrimp Mineral GH/KH+ - Raises both GH and KH for Cherry Shrimp
- SL-Aqua MORE SHRIMP! GH/KH - Taiwanese premium option
For Sulawesi
- Salty Shrimp Sulawesi Mineral 8.5 - For Cardinal Shrimp and Lake Matano species
- Salty Shrimp Sulawesi Mineral 7.5 - For Lake Towuti species
View All Remineralizers to compare products and find the best fit for your setup.
Helpful Calculators
Need help getting your GH levels right? Try these free calculators:
- Remineralization Calculator - Calculate exact remineralizer doses to achieve your target GH and TDS
- Water Change Calculator - Determine water change volumes to adjust GH levels safely
GH by Species Family
Different shrimp families have evolved in different environments, leading to varying gh requirements. Understanding these differences is crucial for successful shrimp keeping.
| Family | Acceptable Range | Optimal Range | Example Species | Notes |
|---|---|---|---|---|
| Neocaridina | 6-12 dGH | 7-9 dGH | Cherry Shrimp | Hardy, tolerates wider ranges |
| Caridina | 4-6 dGH | 5-6 dGH | Crystal Red Shrimp | Sensitive, requires stable parameters |
| Sulawesi | 6-8 dGH | 6-7 dGH | Cardinal Shrimp | Unique requirements, warm alkaline water |
Sensitive, requires stable parameters
Unique requirements, warm alkaline water
Stability Over Perfection
While hitting optimal ranges is ideal, stability is more important than exact numbers. Consistent parameters within the acceptable range are better than fluctuating values that occasionally hit optimal.
How to Test GH
Accurate testing is essential for maintaining proper gh levels. Here are the most common testing methods, each with their own trade-offs.
Liquid Test Kit (Drop Count)
Pros
- Very accurate results
- Shows exact dGH value
- Long shelf life when stored properly
- Industry standard method
Cons
- Takes a few minutes per test
- Requires counting drops carefully
- Reagent bottles can be messy
Test Strips
Pros
- Quick and convenient
- Tests multiple parameters at once
- Good for rough estimates
Cons
- Less accurate than liquid tests
- Color matching can be subjective
- Can expire quickly once opened
Quick Comparison
| Method | Accuracy | Cost | Best For |
|---|---|---|---|
| Liquid Test Kit (Drop Count) | High | $$ | Recommended choice |
| Test Strips | Low | $ | Quick checks |
Testing Tip
Test at the same time of day for consistent results. Water parameters can fluctuate based on feeding, lighting, and CO2 levels. Morning tests before lights-on often provide the most stable readings.
How to Adjust GH
Sometimes you need to adjust your gh levels. Here are safe methods for both raising and lowering values. Always make changes gradually - sudden parameter swings can stress or kill shrimp.
How to Raise GH
Increase gh levels
Remineralizer (GH+ or GH/KH+)
Add Salty Shrimp GH+ (for Caridina) or GH/KH+ (for Neocaridina) to your water change water
Cuttlebone
Add a piece of cuttlebone to slowly release calcium into the water
Crushed Coral
Place in filter or substrate to gradually raise GH and KH
Mineral Stones
Mineral stones designed for shrimp tanks release calcium and magnesium slowly
Warnings
- Crushed coral also raises KH and pH - not suitable for Caridina
- Make changes gradually - sudden GH spikes can trigger bad molts
- Always premix remineralizer before adding to tank
How to Lower GH
Decrease gh levels
RO/DI Water Dilution
Replace tank water with pure RO or DI water to dilute mineral content
Peat Moss Filtration
Filter water through peat moss to bind some minerals
Warnings
- Lowering GH too quickly can trigger molting issues
- Peat moss affects pH and adds tannins - not always desirable
- Never lower GH below species minimum requirements
Critical Safety Notice
Never make sudden, large changes to water parameters. Shrimp are extremely sensitive to parameter swings. All adjustments should be made gradually over hours or days, not minutes. When in doubt, go slower. Test frequently during adjustments to monitor progress.
GH FAQ
GH (General Hardness) measures the concentration of calcium (Ca2+) and magnesium (Mg2+) ions in water. It's measured in degrees of German hardness (dGH) or parts per million (ppm). One dGH equals approximately 17.9 ppm. These minerals are essential for shrimp shell formation and many biological processes.
The White Ring of Death is a white band around a shrimp's body where molting failed partway through. It happens when GH is too low (insufficient calcium for new shell) or when the shrimp is stressed and can't complete the molting process. The old shell gets stuck, the shrimp can't escape, and death usually follows within days.
The ideal Ca:Mg ratio for shrimp is approximately 3:1 to 4:1, mirroring natural freshwater conditions. Most quality shrimp remineralizers are formulated to this ratio. Imbalanced ratios (too much magnesium relative to calcium) can interfere with proper shell formation even if total GH is correct.
Seachem Equilibrium can work for Neocaridina but isn't ideal for shrimp because it contains potassium and iron in addition to calcium and magnesium. For precise control, especially with Caridina, dedicated shrimp remineralizers like Salty Shrimp are preferred as they're specifically formulated for shrimp needs.
GH decreases as shrimp use calcium and magnesium for molting and shell maintenance. Plants also consume these minerals. Each water change with lower-GH water further dilutes the tank. Regular testing and consistent remineralization of water change water maintains stable GH.
No, they're different units. 1 dGH = 17.9 ppm (CaCO3 equivalent). So 6 dGH equals about 107 ppm. Most shrimp keepers use dGH because the numbers are more manageable, but some test kits report ppm. Make sure you know which unit you're reading.
Track Your GH with ShrimpKeeper
Stop guessing. Start tracking. ShrimpKeeper gives you species-specific gh ranges, instant diagnostics, and historical graphs for your colony.
GH Problems & Troubleshooting
Failed Molt: Shrimp Stuck in Shell
CriticalUnderstanding failed molts where shrimp cannot escape their old exoskeleton. Learn why it happens, why affected shrimp cannot be saved, and how to prevent future molt failures.
Shrimp Dying After Water Change
HighWhy shrimp die within hours or days after a water change, and how to perform safe water changes that won't stress or kill your colony.
Why Are My Shrimp Dying?
CriticalComprehensive triage guide for unexplained shrimp deaths. Learn to identify the cause and take immediate action to save your remaining colony.
White Ring of Death in Shrimp
CriticalUnderstanding the dreaded white ring or white line that appears around a shrimp's body, signaling a fatal molting problem that cannot be reversed once visible.